Comparison of efflux rates of hydrogen and lactate ions from isolated muscles in vitro

Relative rates of efflux of hydrogen and lactate ions from skeletal muscle in vitro were determined on isolated rat diaphragms and frog satorius muscles. After a period of lacate accumulation by stimulation in vitro, muscles were suspended in a small volume of Ringer solution for different time periods lasting up to 60 min. The pH change in the solution was monitored continuously. After the predetermined time period, samples of the muscle and the Ringer solution were analysed for lactate content. Results showed that in both types of muscles the rate of efflux of hydrogen ions exceeded that of lactate ions by factors of about 14 and 50 in the case of diaphragm and sartorius muscles respectively. Because of this difference observed in the efflux kinetics of hydrogen and lactate ions, it is evident that the lactate content of a body compartment does not represent the absolute hydrogen ion load of the same compartment, particularly during the early phase of the efflux process.